OB-Gyn: “What is it ma’am, sperm or egg?”

Providing awareness into the sometimes mysterious biology of reproduction, researchers have identified a gene that controls whether the reproductive precursor cells known as germ cells eventually become sperm or eggs.

Researchers in Japan have found a genetic switch that controlling the fate of germ cells. The gene has been identified using a small fish called medaka or Japanese rice fish and is called foxl3. Surprisingly, sperm are produced in the ovaries of females. This sperm function normally and produced normal offspring too.

Though germ cells are present in both sexes of vertebrates, the molecular mechanism that initiates them to develop either sperm or egg has been mysterious.

The researchers found that foxl3 serves as a genetic switch for deciding the sperm-or-egg, the gene is primarily active in a female germ cell to prevent them from becoming sperm cells instead of egg cells in the ovaries.

To confirm, the scientists inactivated the gene in female fish and the germ cells turned into sperm in the Medaka’s ovaries rather than egg cells. Those sperm cells functioned normally, successfully fertilized egg cells and produced healthy offspring.

Humans do not hold the exact same gene, yet the researchers speculate a similar genetic switch mechanism may be at play in people, too.

Minoru Tanaka, a reproductive biologist of Japan’s National Institute for Basic Biology stated nobody knew that in vertebrate’s germ cells have a switch mechanism to decide their own sperm-or-egg fate.

“The germ cells were regarded as passive cells that are regulated by other cells,” added Tanaka, whose research was circulated in the journal Science.

Fellow National Institute for Basic Biology reproductive biologist Toshiya Nishimura added: “In spite of the environment surrounding the germ cells being female, the fact that functional sperm has been made surprised me greatly. That this sexual switch present in the germ cells is independent of the body’s sex is an entirely new finding.”

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